This invention relates to a power generating system and a method of designing the power generating system.
In general, in a photovoltaic power generating system, a plurality of solar cell strings which are formed by coupling a plurality of solar cell modules in series are coupled in parallel in a coupling box, to thereby form a power generating unit. In addition, a plurality of power generating units are coupled in parallel by a power collection rack, and are controlled by a power conditioner so as to be supplied to a system.
Distances between the solar cell strings and the coupling box, and distances between the coupling boxes and the power collection rack are different from one another depending on an installation place of the power collection rack and installation places of the coupling boxes. For this reason, when the coupling is made by using the same kind of electric wire, resistance values of the electric wires are different from one another depending on differences in distance.
In JP 2012-256092 A, which is the background art of this technical field, there is disclosed a photovoltaic power generating system in which a plurality of solar cell generation units are coupled in parallel, and a part or all of total cable lengths of extension cables from the solar cell generation units to the parallel coupling points differ. In this case, the electric resistance values of power transmission paths from the solar cell generation units to the parallel coupling points are controlled to be approximately the same by using a plurality of kinds of extension cables which are different in at least one of an electric resistivity and a conductor cross section.
In addition, the JIS Standard (JIS C 8907) recommends that a loss (array circuit correction coefficient) of a coupling line that is a loss in a DC circuit part including an electric wire and a diode provided within a coupling box are each suppressed within 3%.